Humidity response of single carbon nanocoil and its temperature sensor independent of humidity and strain

Carbon nanocoil (CNC) is a quasi-one dimensional material with unique helical morphology, which provides abundant sites for the adsorption of water and other gas molecules. Herein, we investigated the humidity response of CNCs, including the response mechanism and further regulation. We used several methods to modify the physical and chemical structures of CNC, including 1200 °C annealing, HCl, NH3H2O and H2O2 treatments, to regulate its humidity response and analyze response mechanism. We experimentally demonstrated the p-type conduction of CNCs and the donor characteristic of the adsorbed water molecules, which are not affected by treatment methods. It is found that NH3H2O treatment greatly suppresses the humidity response (almost no response) without affecting the temperature response of CNCs, while annealing suppresses the humidity and temperature response of CNCs simultaneously. Due to the abundant vacancies, defects and functional groups in CNCs, NH3H2O treatment introduces non-volatile water molecules into CNCs, which prevent further adsorption of water molecules and inhibit the humidity response of CNCs. By this way, we achieved an independent temperature sensor of CNCs with no response to humidity, which paves the way for the device based on single CNCs that is independent of humidity and strain.